The purpose of the PREDICTION Trial is to identify high-risk coronary lesions at an early time point in their evolution, to follow the natural history of these lesions over a 6-10 month period, and to confirm that these high-risk lesions are likely to rupture and cause an acute coronary syndrome (ACS) or develop rapid progression of a flow-limiting obstruction. The hypothesis is that local segments in the coronary arteries with low ESS and excessive expansive remodeling will be the sites where atherosclerotic plaque develops, progresses, and becomes high-risk, leading to a new cardiac event. This study is being conducted in Japan as patients are clinically evaluated with followup coronary angiography and IVUS in a routine manner at 6-10 months following their initial percutaneous coronary intervention (PCI) for an ACS.